Thermal conductivity against densityHigher and further left: spreads more heat for its weightThermal expansion against thermal conductivityLower and further right: warps less when heated
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Sources4 documents: Cleveland-Cliffs, Nathan Trotter, National Institute of Standards and Technology, Eastern Alloys
Iron
Cleveland-Cliffs / AK Steel ARMCO Pure Iron Product Data Bulletin (07/2022): Table 1 typical physical properties, Table 2 typical mechanical properties after SRA/recrystallization anneal.
Zinc Zamak 3
Zamak 3 (ASTM B86 die cast), Nathan Trotter (zinc alloy producer) technical data sheet, typical values
1
ARMCO Pure Iron Product Data Bulletin (2022)Cleveland-Cliffsarchived copyIron · Yield strength: typical (0.2% YS), hot rolled + SRA/recrystallization annealIron · Ultimate tensile strength: typical, SRA/recrystallization annealIron · Elongation at break: typical, gauge 4D0Iron · Young's modulus (stiffness): typical, after SRA/recrystallization annealIron · Density: typicalIron · Thermal conductivity: typical at 20 °CIron · Thermal expansion: mean, 20-399 °CIron · Specific heat: typicalIron · Melting point: typical
Elastic Properties of Metals and Alloys, I. Iron, Nickel, and Iron-Nickel Alloys, J. Phys. Chem. Ref. Data 2 (1973)National Institute of Standards and Technologyarchived copyIron · Poisson's ratio: NIST critically evaluated best value (polycrystalline iron)
4
Zinc Die Casting Properties Guide (2012)Eastern AlloysZinc Zamak 3 · Poisson's ratio: typical, Zamak 3 hot-chamber die cast
Each number points to the document that states it, with the exact basis. Values without a number are computed from the sourced ones. "Not sourced" means no citable source states it (or only a specification minimum); figures computed from it are left out too.
Questions
Mechanical
Is Iron stronger than Zinc Zamak 3?
Zinc Zamak 3 is stronger: its yield strength is 221 MPa against 186 MPa for Iron (19%).
Which is lighter, Iron or Zinc Zamak 3?
Zinc Zamak 3 is lighter: 6,600 kg/m³ against 7,860 kg/m³ for Iron.
Which is stiffer, Iron or Zinc Zamak 3?
Iron is stiffer: Young's modulus 207 GPa against 85.5 GPa for Zinc Zamak 3, so the same part in Iron deflects less under the same load.
Which is lighter for the same job, Iron or Zinc Zamak 3?
For the same stiffness or strength: Iron is lighter for a stiff rod or tie (tension), stiff beam (bending), stiff panel or plate; Zinc Zamak 3 is lighter for a strong rod or tie, strong beam, strong panel or plate.
Part that must be
Iron
Zinc Zamak 3
Stiff rod or tie (tension)
lighter
2.03x heavier
Stiff beam (bending)
lighter
31% heavier
Stiff panel or plate
lighter
13% heavier
Strong rod or tie
42% heavier
lighter
Strong beam
34% heavier
lighter
Strong panel or plate
30% heavier
lighter
For the same stiffness or strength, mass scales with density over stiffness (or strength) raised to a power set by how the part is loaded: 1 for a rod in tension, 1/2 for a beam in bending, 1/3 for a panel (the standard material-selection indices).
Which is more ductile, Iron or Zinc Zamak 3?
Iron stretches further before it breaks: 38% elongation at break against 10% for Zinc Zamak 3.
Thermal
Which conducts heat better, Iron or Zinc Zamak 3?
Zinc Zamak 3 conducts heat better: 113 W/m·K against 73.2 W/m·K for Iron.
Which expands less with temperature?
Iron expands less: 13.7 µm/m·K against 27.4 µm/m·K for Zinc Zamak 3.